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Transactions of the American Mathematical Society

Published by the American Mathematical Society since 1900, Transactions of the American Mathematical Society is devoted to longer research articles in all areas of pure and applied mathematics.

ISSN 1088-6850 (online) ISSN 0002-9947 (print)

The 2020 MCQ for Transactions of the American Mathematical Society is 1.48.

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Convergence rate to equilibrium for conservative scattering models on the torus: a new tauberian approach
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by B. Lods and M. Mokhtar-Kharroubi
Trans. Amer. Math. Soc. 377 (2024), 2741-2820
DOI: https://doi.org/10.1090/tran/9087
Published electronically: January 18, 2024

Abstract:

The object of this paper is to provide a new and systematic tauberian approach to quantitative long time behaviour of $C_{0}$-semigroups $\left (\mathcal {V}(t)\right )_{t \geqslant 0}$ in $L^{1}(\mathbb {T}^{d}\times \mathbb {R}^{d})$ governing conservative linear kinetic equations on the torus with general scattering kernel $\boldsymbol {k}(v,v’)$ and degenerate (i.e. not bounded away from zero) collision frequency $\sigma (v)=\int _{\mathbb {R}^{d}}\boldsymbol {k}(v’,v)\boldsymbol {m}(\mathrm {d}v’)$, (with $\boldsymbol {m}(\mathrm {d}v)$ being absolutely continuous with respect to the Lebesgue measure). We show in particular that if $N_{0}$ is the maximal integer $s \geqslant 0$ such that \begin{equation*} \frac {1}{\sigma (\cdot )}\int _{\mathbb {R}^{d}}\boldsymbol {k}(\cdot ,v)\sigma ^{-s}(v)\boldsymbol {m}(\mathrm {d}v) \in L^{\infty }(\mathbb {R}^{d}), \end{equation*} then, for initial datum $f$ such that $\displaystyle \int _{\mathbb {T}^{d}\times \mathbb {R}^{d}}|f(x,v)|\sigma ^{-N_{0}}(v)\mathrm {d}x\boldsymbol {m}(\mathrm {d}v) <\infty$ it holds \begin{equation*} \left \|\mathcal {V}(t)f-\varrho _{f}\Psi \right \|_{L^{1}(\mathbb {T}^{d}\times \mathbb {R}^{d})}=\dfrac {{\varepsilon }_{f}(t)}{(1+t)^{N_{0}-1}}, \qquad \varrho _{f}≔\int _{\mathbb {R}^{d}}f(x,v)\mathrm {d}x\boldsymbol {m}(\mathrm {d}v), \end{equation*} where $\Psi$ is the unique invariant density of $\left (\mathcal {V}(t)\right )_{t \geqslant 0}$ and $\lim _{t\to \infty }{\varepsilon }_{f}(t)=0$. We in particular provide a new criteria of the existence of invariant density. The proof relies on the explicit computation of the time decay of each term of the Dyson-Phillips expansion of $\left (\mathcal {V}(t)\right )_{t \geqslant 0}$ and on suitable smoothness and integrability properties of the trace on the imaginary axis of Laplace transform of remainders of large order of this Dyson-Phillips expansion. Our construction resorts also on collective compactness arguments and provides various technical results of independent interest. Finally, as a by-product of our analysis, we derive essentially sharp “subgeometric” convergence rate for Markov semigroups associated to general transition kernels.
References
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Bibliographic Information
  • B. Lods
  • Affiliation: Department of Economics and Statistics, Università degli Studi di Torino & Collegio Carlo Alberto, Corso Unione Sovietica, 218/bis, 10134 Torino, Italy.
  • MR Author ID: 685939
  • Email: bertrand.lods@unito.it
  • M. Mokhtar-Kharroubi
  • Affiliation: Université de Bourgogne-Franche-Comté, Equipe de Mathématiques, CNRS UMR 6623, 16, route de Gray, 25030 Besançon Cedex, France
  • MR Author ID: 200061
  • Email: mustapha.mokhtar-kharroubi@univ-fcomte.fr
  • Received by editor(s): July 18, 2022
  • Received by editor(s) in revised form: October 23, 2023
  • Published electronically: January 18, 2024
  • Additional Notes: The first author was financially supported by the Italian Ministry of Education, University and Research (MIUR), Dipartimenti di Eccellenza grant 2022-2027 as well as by the de Castro Statistics Initiative, Collegio Carlo Alberto (Torino).
  • © Copyright 2024 American Mathematical Society
  • Journal: Trans. Amer. Math. Soc. 377 (2024), 2741-2820
  • MSC (2020): Primary 82C40; Secondary 35F15, 47D06
  • DOI: https://doi.org/10.1090/tran/9087